What field of PE Header tells that whether a valid PE file or not?

[Bsbosa.com]

Hello,

I need to check that whether a given binary is a valid PE file (Perhaps might some one can rename java file/class file or .js/html files to .exe or .DLL ). In this case i suspect that e_magic field of FileHeader structure would tell this..

or any other field will let the user know about the validity of PE file?

Regards
Usman